Methods and Systems for Orthogonal Frequency Division Multiplexing (OFDM) Multiple Zone Partitioning

ABSTRACT

Aspects of the invention include methods and devices for inserting data and pilot symbols into Orthogonal Frequency Division Multiplexing (OFDM) frames having a time domain and a frequency domain. A method involves inserting in at least one zone of a first type a two dimensional array of data and pilot symbols in time and frequency and inserting in at least one zone of a second type a two dimensional array of data and pilot symbols in time and frequency. In some implementations the zone of the first type comprises common pilot symbols that can be detected by all receivers receiving the OFDM frame. In some implementations the zone of the second type comprises dedicated pilot symbols that are only detectable by a receiver that is aware of pre-processing used to encode the dedicated pilot symbols.

PRIORITY CLAIM

This application is a continuation of and claims the benefit of priorityfrom U.S. patent application Ser. No. 14/458,131, entitled “Methods andSystems for Orthogonal Frequency Division Multiplexing (OFDM) MultipleZone Partitioning” and filed on Aug. 12, 2014, which is a continuationof and claims the benefit of priority from U.S. patent application Ser.No. 13/944,010, entitled “Methods and Systems for Orthogonal FrequencyDivision Multiplexing (OFDM) Multiple Zone Partitioning” and filed onJul. 17, 2013 (issued as U.S. Pat. No. 8,811,544 on Aug. 19, 2014),which is a continuation of and claims the benefit of priority from U.S.patent application Ser. No. 13/292,643, entitled “Methods and Systemsfor Orthogonal Frequency Division Multiplexing (OFDM) Multiple ZonePartitioning” and filed on Nov. 9, 2011 (issued as U.S. Pat. No.8,542,771 on Sep. 24, 2013), which is a continuation of and claims thebenefit of priority from U.S. patent application Ser. No. 12/064,563,entitled “Methods and Systems for Orthogonal Frequency DivisionMultiplexing (OFDM) Multiple Zone Partitioning” and filed on Feb. 22,2008 (issued as U.S. Pat. No. 8,073,063 on Dec. 6, 2011), which is aNational Stage of and claims the benefit of priority fromPCT/CA2006/001383, entitled “Methods and Systems for OFDM Multiple ZonePartitioning” and filed on Aug. 23, 2006, which claims the benefit ofpriority from U.S. Provisional Patent Application No. 60/710,527,entitled “OFDMA Systems and Methods” and filed on filed on Aug. 23,2005, all of which are fully incorporated herein by reference for allpurposes.

BACKGROUND

1. Field of the Application

The invention relates to the field of wireless communications. Morespecifically, the invention relates to OFDM air interfaces.

2. Background of the Disclosure

Orthogonal frequency division multiplexing (OFDM) is a form ofmultiplexing that distributes data over a number of carriers that have avery precise spacing in the frequency domain. The precise spacing andpartially overlapping spectra of the carriers provides several benefitssuch as high spectral efficiency, resiliency to radio frequencyinterference and lower multi-path distortion. Due to its beneficialproperties and superior performance in multi-path fading wirelesschannels, OFDM has been identified as a useful technique in the area ofhigh data-rate wireless communication, for example wireless metropolitanarea networks (MAN). Wireless MAN are networks to be implemented over anair interface for fixed, portable, and mobile broadband access systems.

In an OFDM system, a pilot channel is usually used to obtaintransmission channel information to enable coherent detection. One typeof pilot channel is a common pilot channel that is used by alltransmitters and receivers in a telecommunication cell. Another type ofpilot channel is a dedicated pilot channel that is used by transmittersand can only be detected by receivers to which the pilot channel isdirected. These two types of pilot channels are currently applied indifferent systems.

SUMMARY

According to a first broad aspect of the invention, there is provided amethod for inserting data and pilot symbols into Orthogonal FrequencyDivision Multiplexing (OFDM) frames for transmission on N transmittingantennas where N≧1, the OFDM frames having a time domain and a frequencydomain, each OFDM frame comprising a plurality of OFDM symbols, themethod comprising: partitioning N OFDM frames to be simultaneouslytransmitted on N antennas into at least two sets of correspondingblocks, each set of corresponding blocks consisting of one block foreach of the N OFDM frames, all the blocks in a given set ofcorresponding blocks having a common size and location; for eachantenna; allocating at least one set of corresponding blocks fortransmission of common pilot symbols and allocating at least one set ofcorresponding blocks for transmission of pilot symbols dedicated to atleast one receiver; in each block of each set of corresponding blocksallocated for transmission of common pilot symbols, inserting a twodimensional array of data and common pilot symbols in time-frequency; ineach block of each set of corresponding blocks allocated fortransmission of pilot symbols dedicated to at least one receiver,inserting a two dimensional array of data and pilot symbols dedicated tothe at least one receiver in time-frequency.

In some embodiments the method further comprises performingpre-processing of pilot symbols dedicated to the at least one receiverto encode the pilot symbols for detection by only the at least onereceiver.

In some embodiments partitioning N OFDM frames to be simultaneouslytransmitted on N antennas into at least two sets of corresponding blocksis based on time division multiplexing (TDM).

In some embodiments partitioning N OFDM frames to be simultaneouslytransmitted on N antennas into at least two sets of corresponding blocksis based on frequency division multiplexing (FDM).

In some embodiments partitioning N OFDM frames to be simultaneouslytransmitted on N antennas into at least two sets of corresponding blocksis based on combined TDM/FDM.

In some embodiments the method further comprises inserting controlinformation in a control channel formed in at least one OFDM symbolduration in each set of corresponding blocks.

In some embodiments the control information in each set of blockscomprises one of a group consisting of: a set of blocks for transmissionof common pilot symbols; a set of blocks for transmission of dedicatedpilot symbols; and a set of blocks for transmission of both common pilotsymbols and dedicated pilot symbols.

In some embodiments in each block of each set of corresponding blocksallocated for transmission of common pilot symbols, inserting a twodimensional array of data and common pilot symbols in time-frequencycomprises inserting a common pilot symbol and nulls corresponding tolocations of common pilot symbols of each other block of the set ofcorresponding blocks.

In some embodiments in each block of each set of corresponding blocksallocated for transmission of common pilot symbols, inserting a twodimensional array of data and common pilot symbols in time-frequencycomprises inserting at least one common pilot symbol and nulls in one orboth of: a control channel portion and a data symbol portion of eachblock.

In some embodiments in each block of each set of corresponding blocksallocated for transmission of dedicated pilot symbols, inserting a twodimensional array of data and common pilot symbols in time-frequencycomprises inserting a dedicated pilot symbol and inserting nulls inlocations in time-frequency corresponding to locations of dedicatedpilot symbols of each other block of the set of corresponding blocks.

In some embodiments in each block of each set of corresponding blocksallocated for transmission of dedicated pilot symbols, inserting a twodimensional array of data and dedicated pilot symbols in time-frequencycomprises inserting at least one dedicated pilot symbol and nulls in oneor both of: a control channel portion and a data symbol portion of eachblock.

In some embodiments in each block of a respective OFDM symbol allocatedfor transmission of common pilot symbols, inserting a two dimensionalarray of data and common pilot symbols in time-frequency comprisesinserting collectively at least one common pilot symbol and nulls inlocations in time-frequency corresponding to locations of common pilotsymbols of each other block of the set of corresponding blocks with acommon pattern; and in each block of a respective OFDM symbol allocatedfor transmission of dedicated pilot symbols, inserting a two dimensionalarray of data and dedicated pilot symbols in time-frequency comprisesinserting collectively at least one dedicated pilot symbol and nulls inlocations in time-frequency corresponding to locations of dedicatedpilot symbols of each other block of the set of corresponding blockswith a common pattern.

In some embodiments the common pattern for the at least one common pilotsymbol and nulls is the same common pattern for the at least onededicated pilot symbol and nulls.

In some embodiments the same common pattern is a diagonal shapedlattice.

In some embodiments the common pattern for the at least one common pilotsymbol and nulls is a different common pattern than for the at least onededicated pilot symbol and nulls.

In some embodiments inserting a two dimensional array of data and commonpilot symbols in time-frequency comprises inserting data and commonpilot symbols encoded for transmission using an open loop orthogonalfrequency division multiplexing (OFDM) MIMO (multiple input multipleoutput) format.

In some embodiments inserting a two dimensional array of data and pilotsymbols dedicated to the at least one receiver in time-frequencycomprises inserting data and dedicated pilot symbols encoded fortransmission using a closed loop OFDM MIMO beam forming format.

In some embodiments the method further comprises: setting a transmissionpower for transmitting data symbols and common pilot symbols in sets ofcorresponding blocks allocated for transmission of common pilot symbols;setting a transmission power for transmitting data symbols and dedicatedpilot symbols in sets of corresponding blocks allocated for transmissionof dedicated pilot symbols.

In some embodiments the transmission power for transmitting data symbolsand common pilot symbols is different than transmission power fortransmitting data symbols and dedicated pilot symbols.

In some embodiments the transmission power used for transmitting datasymbols and dedicated pilot symbols is dynamically configurable.

In some embodiments the method further comprises inserting common pilotsymbols in the at least one set of corresponding blocks for transmissionof dedicated pilot symbols.

In some embodiments the method further comprises: for at least oneantenna, in at least one block of a set of corresponding blocksallocated for transmission of dedicated pilot symbols, inserting alarger number of dedicated pilot symbols than are inserted in otherblocks of the set of corresponding blocks of other antennas.

In some embodiments each block in each set of corresponding blockscomprises an odd number of OFDM symbols.

In some embodiments the common size of all blocks in each set ofcorresponding blocks is dynamically configurable.

According to a second aspect of the invention, there is provided an OFDMtransmitter comprising: N transmitting antennas where N≧1, fortransmitting OFDM frames having a time domain and a frequency domain,each OFDM frame comprising a plurality of OFDM symbols; space-timecoding (STC) logic adapted to: partition N OFDM frames to besimultaneously transmitted on the N transmitting antennas into at leasttwo sets of corresponding blocks, each set of corresponding blocksconsisting of one block for each of the N OFDM frames, all the blocks ina given set of corresponding blocks having a common size and location;and for each of the N transmitting antennas the space-time coding (STC)logic adapted to: allocate at least one set of corresponding blocks fortransmission of common pilot symbols and allocate at least one set ofcorresponding blocks for transmission of pilot symbols dedicated to atleast one receiver; insert a two dimensional array of data and commonpilot symbols in time-frequency in each block of each set ofcorresponding blocks for transmission of common pilot symbols; insert atwo dimensional array of data and pilot symbols dedicated to the atleast one receiver in time-frequency in each block of each set ofcorresponding blocks for transmission of pilot symbols dedicated to atleast one receiver.

In some embodiments the OFDM transmitter is adapted to transmit onepilot per antenna arranged in a two by two time-frequency block for afour antenna structure.

The broad aspects described above it is stated that the number oftransmitting antennas is equal to N where, N≧1. In some embodiments ofthe invention N=2. In some embodiments of the invention N=4.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures. TBD

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theattached drawings in which:

FIG. 1A is a flowchart of a method by which data symbols and pilotsymbols are inserted into an OFDM frame according to an embodiment ofthe invention;

FIG. 1B is a flowchart of a method by which data symbols and pilotsymbols are inserted into an OFDM frame according to another embodimentof the invention;

FIG. 2 is a schematic diagram of a time division multiplexing (TDM)Based Zone Partition arrangement for a common pilot zone and a dedicatedpilot zone according to an embodiment of the invention;

FIG. 3 is a schematic diagram of a TDM Based Zone Partition arrangementfor transmission according to an embodiment of the invention for a MIMOzone and a beam forming zone;

FIG. 4 is a further schematic diagram of a TDM Based Zone Partitionarrangement for transmission according to an embodiment of the inventionfor a MIMO zone and a beam forming zone;

FIG. 5 is a schematic diagram of a frequency division multiplexing (FDM)Based Zone Partition arrangement for a common pilot zone and a dedicatedpilot zone according to an embodiment of the invention;

FIG. 6 is a schematic diagram of a FDM Based Zone Partition arrangementfor transmission according to an embodiment for a MIMO zone and a beamforming zone;

FIG. 7 is a schematic diagram of a combined TDM/FDM Based Zone Partitionarrangement for a common pilot zone and a dedicated pilot zone accordingto an embodiment;

FIG. 8 is a block diagram of a cellular communication system;

FIG. 9 is a block diagram of an example base station that might be usedto implement some embodiments of the present invention;

FIG. 10 is a block diagram of an example wireless terminal that might beused to implement some embodiments of the present invention;

FIG. 11 is a block diagram of a logical breakdown of an example OFDMtransmitter architecture that might be used to implement someembodiments of the present invention; and

FIG. 12 is a block diagram of a logical breakdown of an example OFDMreceiver architecture that might be used to implement some embodimentsof the present invention.

DETAILED DESCRIPTION

According to an aspect of the invention, there is provided a method forinserting data and pilot information into Orthogonal Frequency DivisionMultiplexing (OFDM) frames, each frame having a time domain and afrequency domain and including at least one OFDM symbol. With referenceto FIG. 1A, the method will be discussed in further detail. FIG. 1Aillustrates a flow chart for performing the method.

In some embodiments the method is used for creating time-frequencypatterns for transmitting from a base station on one or moretransmitting antennas to one or more receivers, which may have one ormore antenna. An example of a receiver is a mobile station (MS). In someembodiments a mobile station is a wireless device such as a cellulartelephone, computer with a wireless modem, or personal digital assistant(PDA). In some implementations the receiver has a fixed location. Inother implementations the receiver is nomadic or mobile.

A first step 310 involves partitioning N OFDM frames to besimultaneously transmitted on N antennas into at least two sets ofcorresponding blocks, each set of corresponding blocks consisting of oneblock for each of the N OFDM frames, all the blocks in a given set ofcorresponding blocks having a common size and location. A second step320 involves for each antenna allocating at least one set ofcorresponding blocks for transmission of common pilot symbols andallocating at least one set of corresponding blocks for transmission ofpilot symbols dedicated to at least one receiver. A third step 330involves, for each antenna in each block of each set of correspondingblocks allocated for transmission of common pilot symbols, inserting atwo dimensional array of data and common pilot symbols intime-frequency. A fourth step 340 involves, for each antenna in eachblock of each set of corresponding blocks allocated for transmission ofpilot symbols dedicated to at least one receiver, inserting a twodimensional array of data and pilot symbols dedicated to the at leastone receiver in time-frequency.

Generally, within the description each set of corresponding blocks isreferred to as a zone. Therefore, a first set of corresponding blocksallocated for transmission of common pilot symbols may be referred to asa common pilot symbol zone and a second set of corresponding blocksallocated for transmission of dedicated pilot symbols may be referred toas a dedicated pilot symbol zone. In an event an OFDM frame includesmultiple occurrences of the first and/or second set of correspondingblocks, the multiple occurrences are collectively referred to as being acommon pilot symbol zone or dedicated pilot symbol zone, respectively.

A common pilot symbol is a pilot symbol that has been encoded by thetransmitter in such a manner that any receiver receiving the pilotsymbols is capable of determining that the received symbol at aparticular location in time-frequency is a pilot symbol and can use thepilot symbol accordingly.

A dedicated pilot symbol is a pilot symbol that has undergonepre-processing and has been encoded by the transmitter in such a mannerthat only a particular receiver or receivers that are aware of theparticular pre-processing used to encode the pilot symbol is/are capableof determining that the symbol at a particular location intime-frequency is a pilot symbol and can use the pilot symbolaccordingly.

In some embodiments common pilot symbols may be included in the blocksthat have predominantly dedicated pilot symbols to allow receivers notcapable of detecting the dedicated pilot symbol an opportunity todetermine channel quality measurements in those blocks.

FIG. 1B shows a flow chart for a method according to another embodimentof inserting data and pilot information into Orthogonal FrequencyDivision Multiplexing (OFDM) frames in which steps 310, 320, 330 and 340are the same as in FIG. 1A. An additional step in the method is step350, which involves setting the transmission power for blocks allocatedfor common pilot symbols. Step 360, involves setting the transmissionpower for blocks allocated for dedicated pilot symbols. In someembodiments the transmission power for the blocks allocated for commonpilot symbols is the same for blocks allocated for dedicated pilotsymbols. In some embodiments the transmission power for the blocksallocated for common pilot symbols is different than for blocksallocated for dedicated pilot symbols. In some embodiments, thetransmission power is set the same for both data symbols and pilotssymbols in the blocks allocated for common pilot symbols. In someembodiments, the transmission power is set the same for both datasymbols and pilots symbols in the blocks allocated for dedicated pilotsymbols. In some embodiments the transmission power is set differentlyfor data symbols than for pilots symbols in the blocks allocated forcommon pilot symbols. In some embodiments the transmission power is setdifferently for data symbols than for pilots symbols in the blocksallocated for common pilot symbols.

In some embodiments a power control ratio between data symbols and pilotsymbols is maintained to ensure consistent channel estimates for allreceivers. The use of zones allocated for transmission of common pilotsymbols and zones allocated for transmission of dedicated pilot symbolsallows for varying transmission power to different receivers, whilemaintaining the power control ratio for a given receiver. For zonesusing common pilot symbols, the data symbols for different respectivereceivers and the common pilot symbols used for all receivers maintain aconsistent power control ratio by maintaining a constant transmissionpower because the common pilot symbols are all transmitted with aconstant proportional power level to that of the data symbols for therespective receivers. For zones using dedicated pilot symbols, the datasymbol transmit power for different respective receivers can beincreased or decreased as well as the dedicated pilot symbols associatedwith those different respective receivers and therefore each respectivereceiver maintains a consistent power control ratio. In someembodiments, receivers that require a larger transmission power for bothdata and pilots, for example receivers that are geographically locatedat the edge of a communication cell, are attended to by using adifferent transmission zone than receivers in closer proximity to thetransmitter. In some embodiments the zones allocated for transmission ofdedicated pilot symbols have a different transmission power for datasymbols and pilot symbols than a transmission power used for datasymbols and pilot symbols transmitted in zones allocated fortransmission of common pilot symbols.

In some embodiments the data symbol and the pilot symbol transmissionpowers respectively, can be increased in the dedicated pilot symbol zonesuch that the power control ratio is maintained. Only receivers that areaware of the pre-processing used to encode the dedicated pilots arecapable of using the dedicated pilots for channel estimation becausethose receivers are aware of the pre-processing used to encode thededicated pilots.

In some embodiments a zone allocated for transmission of common pilotsymbols is used to transmit to receivers within range of the transmitterthat maintain an acceptable quality of received transmission. Allreceivers are capable of using the common pilots for channel estimationbecause the pre-processing used to encode the common pilots is known toall receivers.

In some embodiments an additional number of dedicated pilots may beinserted in the zone allocated for transmission of dedicated pilotsymbols for one or more antennas. For example, this may be performed atstep 340 of FIG. 1A or FIG. 1B. An additional number of dedicated pilotsmay be advantageous in the above-described example in which the receiveris at the edge of a communication cell and extra pilots would enable abetter estimate of the channel between transmitter and receiver.

In some embodiments, in zones allocated for transmission of common pilotsymbols having a known location sequence, in select zones an additionalnumber of pilot sub-carriers are inserted between two known locationcommon pilot symbols to increase the density of the pilots to enable abetter estimate of the channel between transmitter and receiver.

In some embodiments, a pattern used in zones allocated for common pilotsymbols is a same pattern used in zones allocated for dedicated pilotsymbol.

Various examples of OFDM frames having particular time-frequencypatterns with zone partitioning formed using the method described abovewill be described in detail below with regard to FIGS. 2 to 7.

FIG. 2 shows an example time division multiplexing (TDM) Based ZonePartition pattern 600 employed for transmitting data and pilot symbols.The TDM Based Zone Partition pattern 600 is shown having a twodimensional appearance in which the horizontal direction 604 isfrequency and the vertical direction 602 is time. In the frequencydirection, each discrete vertical column represents a singlesub-carrier. Each discrete horizontal row represents an OFDM symbol.

In the example of FIG. 2, each OFDM symbol is shown to utilize theentire allocated frequency spectrum. The allocated frequency spectrum isformed from multiple adjacent sub-carriers.

FIG. 2 illustrates an embodiment in which an OFDM frame is the entireTDM Based Zone Partition pattern 600. The OFDM frame is partitioned intothree blocks 640,641,642. The three blocks are allocated to a zone fortransmission of data and common pilot symbols and a zone fortransmission of data and pilot symbols dedicated to at least onereceiver, or dedicated pilots. In the illustrated example blocks 640,642constitute a first zone 610 for transmission of common pilot symbols andblocks 641 constitutes a second zone 620 for transmission of dedicatedpilot symbols. An OFDM transmission frame includes at least one of eachtype of zone.

In some embodiments, multiple antennas each transmit a respectivecorresponding OFDM frame, in which each corresponding OFDM frame ispartitioned into a corresponding number of blocks. Each set ofcorresponding blocks consists of one block for each of the correspondingOFDM frames. All of the blocks in a given set of corresponding blockshave a common size and location in the corresponding OFDM frames. Thesets of blocks are either designated as a first zone or a second zone.In some embodiments the first zone is for transmission of data andcommon pilot symbols. In some embodiments the second zone is fortransmission of data and dedicated pilot symbols.

In some embodiments partitioning of the OFDM frame is based on dividingthe frame into multiple blocks and assigning each block to either afirst or second zone. In some embodiments these block may be alignedwith transmission time intervals (TTI). For example, in FIG. 2 theblocks 640, 641, 642 are consistent with a TTI definition in which eachblock includes a single TTI having seven OFDM symbols. In someembodiments the multiple TTIs each have an equal duration. For example,a frame having a duration equal to 10 ms may include five TTIs, whichare each 2 ms in duration. More generally, the number of TTIs in a frameis implementation specific. In some embodiments the number of TTIs inthe frame and their respective durations are dynamically configurable.Once the number and duration of TTIs is set in the frame the respectivedurations of the TTIs remain the same until they are reconfigured.

The number of TTI in either type of zone is one or more. Furthermore,the number of TTI in different types of zones may or may not be equal.

The TTI in the TDM Based Zone Partition pattern 600 are formed fromseven OFDM symbols each. In some embodiments, the TTI in either type ofzone comprise an odd number of OFDM symbols per TTI in accordance with3GPP TR 25.814 v0.1.1 (June 2005). More generally, the number of OFDMsymbols per TTI is implementation specific and may be more or less thanthe seven OFDM symbols shown in FIG. 2.

A first OFDM symbol in each TTI is illustrated to include controlinformation in the form of a control channel 630 for each respectiveTTI. The control channel 630 may be used for transmitting controlinformation from the transmitter to the receiver pertaining tocontrolling the link between the transmitter and receiver. For example,the control channel may include synchronization information or DL or ULMAP information. The remainder of the six OFDM symbols in each TTIinclude data and pilot symbols to be transmitted from the transmitter tothe receiver. While only three control channels are shown in FIG. 2 itis to be understood that the number of control channels may be dependentupon the size of the TTI and the number of TTI in a frame.

In some embodiments pilot symbols, common or dedicated, are transmittedin only the OFDM symbol containing control channel information for eachzone. In some embodiments pilot symbols, common or dedicated, aretransmitted in only portions of the zone containing transmission datasymbols. In some embodiments pilot symbols, common or dedicated aretransmitted in both a control channel portion and the portions of thezone containing data symbols.

It is to be understood that the position of the control channel isimplementation specific and is not limited to a first OFDM symbollocation of each TTI as shown in FIG. 2. In some embodiments, thecontrol channel is located at the same location in the TTI for each TTIin the TDM Based Zone Partition pattern. In some embodiments, thecontrol channel is located in a different location in the TTI for eachdifferent zone in the TDM Based Zone Partition pattern. In someembodiments, in a same zone the control channel is located at adifferent position in one or more TTI of the same frame.

In OFDM transmission, MIMO (multiple input multiple output) transmissioninvolves a one or more transmitters each having multiple antennascommunicating with one or more receivers each having multiple antennas.Each transmitting antenna/receiving antenna path occurs over a channelhaving a particular channel characteristic. In some embodiments, OFDMMIMO transmission is implemented as an open loop type of transmission inwhich channel characteristics between a given transmitting and receivingantenna are unknown at the time of transmission. When channelcharacteristics are known for a channel between a given transmitting andreceiving antenna, these known channel characteristics can be used tooptimize the transmission from transmitter to receiver. One manner tooptimize the transmission is to pre-process the signal to be transmittedin a manner that helps to compensate for the known channelcharacteristics. In some embodiments, this includes providing differentweights to data and pilot symbols in different transmitting antennasknown as beam forming. When channel characteristics are known and usedfor compensation, this is generally referred to as a closed loop type ofMIMO transmission.

In some embodiments a first zone, for example 610 in FIG. 2 is allocatedfor transmission of common pilot symbols is used for transmission ofdata and common pilot symbols using a first MIMO format, for example anopen loop OFDM MIMO as described above. In some embodiments a secondzone, for example 620 in FIG. 2 is allocated for transmission ofdedicated pilot symbols is used for transmission of data and dedicatedpilot symbols using a second MIMO format, for example OFDM beam forming.Beam forming in this context refers to pre-processing of an OFDM MIMOtransmission in a closed loop manner as described for example, above. Itis to be understood that open loop MIMO and closed loop MIMO beamforming are only two examples of MIMO transmission formats that can beused for transmitting common pilot symbols and dedicated pilot symbols,respectively and that these two transmission formats is not intended tolimit the scope of the invention. Additional examples of types of MIMOformats include, but are not limited to: Blast, SM (spatialmultiplexing) and STTD (space-time transmit diversity).

In some embodiments a MIMO format may be selected for the dedicatedpilot symbol zone for implementing power control transmissions in whichonly one or more particular receivers are being communicated.

FIG. 2 shows blocks in each zone equal to one TTI having seven OFDMsymbols, alternating one after another, however it is to be understoodthat the arrangement of the TTI in the different zones is implementationspecific. In some implementations a first zone, including several TTIallocated for transmission of common pilot symbols, each TTI having asame number of OFDM symbols, is transmitted before a second zoneincluding several TTI allocated for transmission of dedicated pilotsymbols is transmitted. In some embodiments the arrangement of zoneswith TTI having the same number of OFDM symbols is periodic in theframe. In some embodiments the arrangement of zones allocated fortransmission of common or dedicated pilot symbols, respectively is notperiodic, but is arranged based on a desired usage of common ordedicated pilot symbols by the transmitter. In some embodiments adjacentzones have a different number of TTI and maintain a repeating pattern ofalternating types of zones even though a ratio of transmission of TTI ina zone allocated for transmission of common pilot symbols to TTI in azone allocated for transmission of dedicated pilot symbols is greaterthan or lesser than if the zones were the same size.

In some embodiments, data being transmitted from a transmitter isencoded using pre-processing techniques that increase a Channel QualityIndicator (CQI) value to optimize transmission energy for a particularreceiver. In some embodiments the particular receiver or receivers areprovided with a knowledge of the pre-processing technique used to encodethe dedicated pilot symbols prior to the pilot symbols beingtransmitted. This can be performed in a similar manner to how thereceiver is notified of the pre-processing technique used for encodingdata that is specific to a receiver so that other receivers cannotdecode data directed to that receiver.

An example of a pre-processing technique used to encode data in adedicated pilot zone is generating a pre-processing matrix defining thetransmission characteristics for transmission to a particular receiveror receivers. For example, in beam forming, pre-processing may involveelements in the pre-processing matrix being weighted to compensate forknown channel conditions. The pre-processing matrix is applied to thedata by the transmitter following which the pre-processed data istransmitted to one or more receivers. In some embodiments dedicatedpilot symbols are encoded in a similar manner to the data in thededicated pilot symbol zone.

In some embodiments, when the transmitter is responsible for determiningthe pre-processing matrix used to encode the data in the dedicated pilotsymbol zone, the transmitter sends information defining the type ofpre-processing to the receiver on a signaling channel so that thereceiver will be able to detect the pre-processed data. A signalingchannel may be included in control channel information on the controlchannel. In some embodiments, the receiver can decode the pre-processeddata based on received dedicated pilot symbols that have been encoded ina similar fashion to the data.

In some embodiments, when the receiver is responsible for thedetermining the pre-processing matrix used to encode the dedicated pilotinformation the receiver sends this information to the transmitter sothat the transmitter can encode the dedicated pilot symbols in themanner desired by the receiver.

FIG. 3 shows an example TDM Based Zone Partition pattern 700 employedfor transmitting data and pilots in a transmitter with four antennas.The TDM Based Zone Partition pattern 700 is shown having a twodimensional appearance in which the horizontal direction is frequencyand the vertical direction is time. Each vertical column represents asingle sub-carrier. Each horizontal row represents an OFDM symbol.

The example TDM Based Zone Partition pattern 700 shows the combined dataand pilot pattern for all four antennas. The pattern transmitted by agiven antenna includes the data in locations common to all the antennasand pilot symbols for transmission only by the given antenna. A groupingof pilot symbols shown in FIG. 3 would, for example be represented in agiven antenna pattern by the pilot symbol for the given antenna and nullsymbol locations for each other antenna. The data and pilots in eachzone may be intended for one or more receivers that are currently withinthe cell of the transmitter.

FIG. 3 illustrates an embodiment of the invention in which a first zone710 allocated for transmission of common pilot symbols is shown to befor OFDM MIMO transmission and a second zone 720 allocated fortransmission of dedicated pilot symbols is shown to be for OFDM beamforming transmission.

While the second zone with dedicated pilots in the illustrated exampleis described to be for OFDM beam forming transmission, this is not meantto limit the scope of the invention to only this type of transmission.

Individual zones in the TDM Based Zone Partition pattern 700 are formedfrom one or more TTI having seven OFDM symbols each. In someembodiments, the first zone 710 and the second zone 720 have TTI with anodd number of OFDM symbols in accordance with 3GPP TR 25.814 v0.1.1(June 2005). More generally, the number of OFDM symbols per TTI isimplementation specific and may be more or less than the seven OFDMsymbols that are shown in the respective TTI of FIG. 3. Also, the numberof TTI per zone is implementation specific.

A first OFDM symbol in each respective TTI is a control channel 730 forthat TTI. It is to be understood that the position of the controlchannel is implementation specific and is not limited to a first OFDMsymbol location of each TTI as shown in FIG. 3. In some embodiments, thecontrol channel is located at the same location of the TTI for each zonein the TDM Based Zone Partition pattern. In some embodiments, thecontrol channel is located in a different location of a TTI fordifferent zones in the TDM Based Zone Partition pattern. In someembodiments, in a same zone the control channel is located at adifferent position in one or more TTI of the same frame. While only fourcontrol channels are shown in FIG. 3 it is to be understood that in someembodiments the number of control channels is dependent upon the size ofTTI and/or the number of TTI in a frame.

The example of FIG. 3 illustrates pilot symbols that are allocated toboth an OFDM symbol including the control channel 730 and the portionsof the TTI containing data symbols in each respective TTI. In someembodiments pilot information is transmitted in only the OFDM symbolincluding the control channel 730 for each respective TTI. In someembodiments pilot information is transmitted in only the portions of theTTI containing data symbols. In some embodiments pilot information istransmitted in both the OFDM symbol including the control channel andthe portions of the TTI containing data symbols.

The TDM Based Zone Partition pattern 700 includes groupings of fourpilot symbols 740,750, one symbol for each antenna. For the first zone710, the OFDM MIMO zone, the pilot symbols are common pilot symbols 740so that any receiver can receive and detect the pilot symbols in thiszone. For the second zone 720, the OFDM Beam forming zone, the pilotsymbols are dedicated pilot symbols 750 so that only receivers aware ofthe pre-processing technique used on the pilots utilize the dedicatedpilot symbols in this zone.

In FIG. 3, in the time direction there are two consecutive seven OFDMsymbol MIMO TTI, each TTI consisting of a number of MIMO transmissionblocks (for example, 12 sub-carriers by 7 OFDM symbols), followed by twoconsecutive beam forming transmission TTI. The pattern is also repeatedin the frequency direction with a twelve subcarrier period. Moregenerally, an arrangement in the time direction for a first zone and asecond zone is implementation specific and may include any number of TTIallocated for transmission of common pilot symbols followed by anynumber of TTI allocated for transmission of dedicated pilot symbols. Insome embodiments this pattern repeats multiple times for a frame. Insome embodiments an alternating pattern of zones have a different numberof TTI adjacent to one another for each respective occurrence of eachtype of zone. Similarly, in the frequency direction, the period of thepattern is implementation specific and may include a period having anynumber of TTI.

For each seven OFDM symbol by twelve subcarrier transmission block,either MIMO zone or beam forming zone, FIG. 3 shows two groupings ofpilot symbols 740,750. The groupings of pilot symbols, both common anddedicated are shown to be a two subcarrier by two symbol duration (ortwo by two time-frequency) grouping. It is to be understood by thoseskilled in the art that other patterns for the grouping of pilot symbolsmay be used. For example, other patterns may include a single subcarrierby four symbol duration grouping or a four subcarrier by single symbolduration grouping. In some embodiments a grouping of pilot symbols isone in which only some of the pilot symbols are directly adjacent to oneanother. In some embodiments a grouping of pilot symbols is one in whichnone of the pilot symbols are directly adjacent to one another.

In FIG. 3 there are two groupings of pilot symbols per seven OFDM symbolby twelve subcarrier transmission block for both the common anddedicated pilot patterns in the first zone 710 and in the second zone720, respectively. If is to be understood that the number of pilotsymbol groupings is implementation specific and not to be limited by theexample embodiment.

In the illustrated embodiment, in the first zone 710, the groupings ofcommon pilot symbols 740 are inserted in a diamond lattice pattern overthe two consecutive TTI in the time direction. Similarly, in the secondzone 720, the groupings of dedicated pilot symbols 750 are insertedusing the same diamond lattice pattern as the pilot groups in the firstzone 710. In the illustrated example four of every seven OFDM symbolscarry encoded pilot symbols, but it is to be understood that dependingon how pilot symbols are inserted in the zones and/or frame that theratio of OFDM symbols having pilot symbols to OFDM symbols not havingpilot symbols may vary.

In some embodiments the diamond lattice pattern in which each groupingof encoded pilot symbols, either common or dedicated is inserted withinthe OFDM frame is a perfect diamond lattice pattern. To achieve this, agrouping of encoded pilot symbols is inserted at each of a first subsetof frequencies. The frequencies within the first subset of frequenciesare spaced equally apart by a pilot spacing. At some later time, agrouping of encoded pilot symbols is inserted at each of a second subsetof frequencies. The frequencies within the second subset of frequenciesare shifted from the frequencies within the first subset of frequenciesby half of the pilot spacing within the frequency direction. Groupingsof pilot symbols are inserted in the frame alternating between the firstsubset of frequencies and the second subset of frequencies.

A different pilot pattern can be used, as long as the same pilot patternis used for each of the pilot symbols corresponding to a particularantenna of the grouping of pilot symbols, and as long as the pilotpatterns for the encoded pilot symbols are offset from each other in thetime direction of the OFDM frame. For example, a diagonal pattern may beused; the diamond shaped lattice being a special case of this.

More generally, any staggered pattern of pilot symbols can be used. Insome embodiments the groupings of pilot symbols are close enoughtogether to ensure that there is time coherence and/or frequencycoherence. Time coherence occurs when pilot symbols in the timedirection are close enough in proximity that channel characteristics aresubstantially the same at the two points in time within an acceptabletolerance. Frequency coherence occurs when pilot symbols in thefrequency direction are close enough in proximity that channelcharacteristics are substantially the same at two sub-carriers within anacceptable tolerance.

In some embodiments the respective pilot patterns that are used in thezone containing common pilot symbols and the zone containing dedicatedpilot symbols are different pilot patterns.

FIG. 3 is described as being for a transmitter with four antennas. It isto be understood that a four antenna transmitter is a particular exampleand not meant to limit the scope of the invention. The number ofantennas in a transmitter is an implementation specific variable. Insome embodiments of the invention the TDM based zone partition patternconcept can be applied to any number of antenna equal to or greater thanone. In some embodiments the number of pilot symbols in a pilot symbolgrouping in the TDM Based Zone Partition patterns is dependent on thenumber of antennas in the transmitter.

FIG. 4 shows another example TDM Based Zone Partition pattern 800employed for transmitting data and pilots in a transmitter with fourantennas. The TDM Based Zone Partition pattern 800 is shown having a twodimensional appearance in which the horizontal direction is frequencyand the vertical direction is time. Each vertical column represents asingle sub-carrier. Each horizontal row represents an OFDM symbol.

The example TDM Based Zone Partition pattern 800 shows the combined dataand pilot pattern for all four antennas. The patterns for eachrespective antenna would represent the data and pilots symbols fortransmission by each respective antenna only. A grouping of pilotsymbols shown in FIG. 4 would, for example be represented in a givenantenna pattern by the pilot symbol for the given antenna and nullsymbol locations for each other antenna. The data and pilots in eachzone may be intended for one or more receivers that are currently withinthe cell of the transmitter.

FIG. 4 illustrates an embodiment in which a first zone 810 is shown tobe for OFDM MIMO transmission and a second zone 820 is shown to be forOFDM beam forming transmission. The TTI utilized in the different zonesof TDM Based Zone Partition pattern 800 are formed from seven OFDMsymbols each. In some embodiments, the first zone and the second zoneeach have TTI with an odd number of OFDM symbols per TTI in accordancewith 3GPP TR 25.814 v0.1.1 (June 2005). More generally, the number ofOFDM symbols is implementation specific and may be more or less than theseven OFDM symbols shown in FIG. 4.

A first OFDM symbol in each respective TTI in the first zone 810 is acontrol channel 830 and a first OFDM symbol in each respective TTI inthe second zone 820 is a control channel 840 for the second zone 820.While only two control channels are shown in FIG. 4 it is to beunderstood that in some embodiments the number of control channels isdependent upon the size of TTI and/or the number of TTI in a frame.

It is to be understood that the position of the control channel isimplementation specific and is not limited to a first symbol locationper TTI as shown in FIG. 4. In some embodiments, the control channel islocated at the same location of the TTI for each zone in the TDM BasedZone Partition pattern. In some embodiments, the control channel islocated in a different location of the TTI for each different zone inthe TDM Based Zone Partition pattern. In some embodiments, in a samezone the control channel is located at a different position in differentTTI of the same frame.

The example of FIG. 4 illustrates a grouping of common pilot symbols 850that are allocated for the first zone 810, the MIMO zone, in the controlchannel 830 of the first zone and a data symbol portion of the firstzone 810 (indicated at 850 a), in the data symbol portion of the firstzone 810 (indicated at 850 b) and also in the control channel 840 and adata symbol portion of the second zone 820 (indicated at 850 c). Agrouping of dedicated pilot symbols 860 is allocated for the second zone820, the beam forming zone and appears only in the data symbol portionof the second zone 820. Overlap of the common pilot symbols from thefirst zone 810 into the second zone 820 enables a diamond latticepattern to occur in zone that is only a single TTI duration in the timedirection. In the particular example of FIG. 4, the groupings of pilotsymbols of the first zone 810 that overlap into the second zone 820 ofthe OFDM frame result in the fact that the second zone 820 does not havea complete diamond lattice pattern of pilot symbols in the single TTI.In some embodiments the transmissions in the second zone have only asmall amount of channel variation over time. Channel estimates can bemade for transmissions having only a small amount of channel variationover time by interpolating the groupings of pilot symbols in the secondzone 820 with groupings of pilot symbols in non-adjacent second zonetransmission blocks.

In some embodiments, all zones in a frame, whether they are one TTI induration or more than one TTI in duration in the time direction, includea diamond lattice pattern that enables using adaptive 2D channelinterpolation as described in assignee's co-pending PCT PatentApplication No. PCT/CA2006/001380, filed on Aug. 22, 2006 which ishereby incorporated by reference in its entirety.

In FIG. 4, in the time direction there is one seven OFDM symbol MIMOtransmission TTI followed by one seven OFDM symbol beam formingtransmission TTI. The TTI contain multiple transmission blocks eachhaving twelve sub-carriers so that a transmission block pattern is alsorepeated in the frequency direction with a twelve subcarrier period.More generally, an arrangement in the time direction for a zoneallocated for transmission of common pilot symbols and a zone allocatedfor transmission of dedicated pilot symbols is implementation specificand may include any number of TTI in a repeating pattern of a zoneallocated for transmission of common pilot symbols followed by anynumber TTI of a zone allocated for transmission of dedicated pilotsymbols. In some embodiments this pattern may repeat multiple times fora frame. In some embodiments, in the time direction an alternatingpattern of different types of zone have a different number of the sameTTI adjacent to one another for each respective occurrence of the typesof zones. Similarly, in the frequency direction the period of thepattern is implementation specific and may include a period having anynumber of TTI.

For each seven OFDM symbol by twelve subcarrier transmission block,either MIMO zone or beam forming zone, FIG. 4 shows two groupings ofpilot symbols 850,860. The groupings of pilot symbols 850,860, bothcommon and dedicated are shown to be a two subcarrier by two symbolduration grouping. It is to be understood by those skilled in the artthat other patterns for the grouping of pilot symbols may be used. Forexample, other patterns may include a single subcarrier by four symbolduration grouping or a four subcarrier by single symbol durationgrouping. In some embodiments a grouping of pilot symbols is one inwhich only some of the pilot symbols are directly adjacent to oneanother. In some embodiments a grouping of pilot symbols is one in whichnone of the pilot symbols are directly adjacent to one another, but areclose enough together to ensure that there is time coherence and/orfrequency coherence.

In some embodiments when the control channel is located in a differentposition than the first OFDM symbol per TTI as shown in FIG. 4, thegrouping of pilot symbols that is shown overlapping into both thecontrol channel and data symbol portion of the second zone in FIG. 4,may only overlap the data symbol portion and not the control channel.

FIG. 4 is described as being for a transmitter with four antennas. It isto be understood that a four antenna transmitter is a particular exampleand not meant to limit the scope of the invention. The number ofantennas in a transmitter is an implementation specific variable. Insome embodiments of the invention the TDM based zone partition patternconcept can be applied to any number of antenna equal to or greater thanone. In some embodiments the number of pilot symbols in a grouping inthe TDM Based Zone Partition pattern is dependent on the number ofantennas in the transmitter.

FIG. 5 shows an example frequency division multiplexing (FDM) Based ZonePartition pattern 900 employed for transmitting data and pilot symbols.The FDM Based Zone Partition pattern 900 is shown having a twodimensional appearance in which the horizontal direction is frequencyand the vertical direction is time. Each discrete vertical columnrepresents a single sub-carrier. Each discrete horizontal row representsan OFDM symbol. In the example of FIG. 5, the FDM Based Zone Partitionpattern 900 is formed of multiple contiguous sub-carriers assigned tomultiple OFDM symbols for a zone allocated for transmission of dedicatedpilot symbols and multiple contiguous sub-carriers assigned to multipleOFDM symbols for a zone allocated for transmission of dedicated pilotsymbols.

In some embodiments partitioning between a zone allocated fortransmission of dedicated pilot symbols and a zone allocated fortransmission of dedicated pilot symbols is based on dividing a frameinto multiple subcarrier portions referred to as sub-bands. In someembodiments the sub-bands each have an equal bandwidth. In someembodiments the number of sub-bands in the frame and their respectivebandwidths are dynamically configurable. Once the number and bandwidthof sub-bands is set in the frame the respective bandwidths of thesub-bands remain the same until they are reconfigured.

The number of sub-bands, or blocks, in either zone is one or more.Furthermore, the number of sub-bands in different zones may or may notbe equal.

A first zone 910 allocated for transmission of common pilot symbols isshown to be for OFDM beam forming transmission and a second zone 920allocated for transmission of dedicated pilot symbols is shown to be forOFDM MIMO transmission.

In the illustrated example, FDM Based Zone Partition pattern 900 has twoOFDM symbols allocated for transmission of control channel informationin control channels 930. The control channel 930 is shown to occuracross the first and second zones of the OFDM frame. The control channel930 is used for transmitting information from the transmitter to thereceiver pertaining to controlling the link between the transmitter andreceiver. For example, the control channel may include synchronizationinformation, DL or UL MAP information. The remainder of the symbols ineach zone include data and pilots to be transmitted from the transmitterto the receiver.

In some embodiments the control channel information is transmitted in atleast one transmission block of only the first zone. In some embodimentsthe control channel information is transmitted in at least onetransmission block of only the second zone.

In some embodiments, pilot symbols, either common or dedicated, aretransmitted in only an OFDM symbol containing control channelinformation for each zone. In some embodiments pilot symbols, common ordedicated are transmitted in only the portions of the zone containingdata symbols. In some embodiments pilot symbols, common or dedicated aretransmitted in both a control channel portion and the portions of thezone containing data symbols.

It is to be understood that the position of the control channel isimplementation specific and is not limited to a periodic OFDM symbolspacing such as that shown in FIG. 5. While only two control channelsare shown in FIG. 5, one per seven OFDM symbol duration per zone it isto be understood that in some embodiments the number of control channelsis dependent upon the duration of OFDM symbols and/or the number of OFDMsymbols in a frame.

FIG. 5 also shows MIMO and beam forming zones having OFDM symboldurations of the same size, alternating one after another in thefrequency direction, however it is to be understood that the arrangementof the zones is implementation specific. In some implementations amultiple sub-bands may be used for one zone than for a different zone.In some embodiments the arrangement of zones is periodic in a frame. Insome embodiments the arrangement of zones is not periodic, but isallocated based on the particular usage of zones by the transmitter.

In some embodiments, receivers that require a larger transmission powerfor both data and pilots, for example receivers that are geographicallylocated at the edge of a communication cell, are attended to by using adifferent transmission zone than receivers in closer proximity to thetransmitter. In some embodiments the second zone has a differenttransmission power for data symbols and pilot symbols than atransmission power used for data symbols and pilot symbols transmittedin the first zone.

In some embodiments an additional number of dedicated pilots may beinserted in the OFDM beam forming zones. For example, this may beadvantageous in the above-described example in which the receiver is atthe edge of a communication cell and extra pilots would enable a betterestimate of the channel between transmitter and receiver.

In some embodiments, a pattern used for common pilot symbols in a firstzone is a same pattern used for dedicated pilot symbols in a secondzone.

In some embodiments common pilot symbols may be included in the blocksthat have predominantly dedicated pilot symbols to allow receivers notcapable of detecting the dedicated pilot symbol an opportunity todetermine channel quality measurements in those blocks.

FIG. 6 shows an example FDM Based Zone Partition pattern 1000 employedfor transmitting data and pilot symbols in a transmitter with fourantennas. The FDM Based Zone Partition pattern 1000 is shown having atwo dimensional appearance in which the horizontal direction isfrequency and the vertical direction is time. Each discrete verticalcolumn represents a single sub-carrier. Each discrete horizontal rowrepresents an OFDM symbol.

The example TDM Based Zone Partition pattern 1000 shows the combineddata and pilot pattern for all four antennas. The patterns for eachrespective antenna would represent the data and pilots symbols fortransmission by each respective antenna only. A grouping of pilotsymbols shown in FIG. 6 would, for example be represented in a givenantenna pattern by the pilot symbol for the given antenna and nullsymbol locations for each other antenna. The data and pilots in eachzone may be intended for one or more receivers that are currently withinthe cell of the transmitter.

FIG. 6 illustrates an embodiment in which a first zone 1010 is for OFDMMIMO transmission and a second zone 1020 is for OFDM beam formingtransmission. Beam forming in this context refers to pre-coding of OFDMMIMO (multiple input multiple output) transmissions. It is to beunderstood that these are examples of two transmission formats that canbe used for transmitting common pilot symbols and dedicated pilotsymbols, respectively and that these two transmission formats is notintended to limit the scope of the invention. For example, dedicatedpilots may be used in conjunction with power control transmissions inwhich only one or more particular receivers are being communicated.

In FIG. 6, each zone in the FDM Based Zone Partition pattern 1000 isformed from sub-bands of twelve sub-carriers. The first zone 1010 is anOFDM MIMO transmission zone formed from two sub-bands. The second zone1020 is an OFDM beam forming transmission zone formed from twosub-bands. More generally, the number of sub-bands per zone isimplementation specific and may be more or less than the two sub-bandsshown in FIG. 6. Also, the number of sub-carriers forming a sub-band isimplementation specific and may be more or less than the twelvesub-carriers shown in FIG. 6. In some embodiments the number ofsub-bands in the first zone may be greater than or less than the numberof sub-bands in the second zone.

The sub-bands are also illustrated to be divided into durations of sevenOFDM symbols in the time direction. In some embodiments, sub-bands aredivided into durations having odd number of OFDM symbols per sub-band inaccordance with 3GPP TR 25.814 v0.1.1 (June 2005). More generally, thenumber of OFDM symbols per sub-band is implementation specific and maybe more or less than the seven OFDM symbols shown in FIG. 6.

In the illustrated example, FDM Based Zone Partition pattern 1000 hasfour OFDM symbols allocated as control channels 1030 for control channelinformation. The control channel is transmitted within both zones. Insome embodiments the control channel information is transmitted in atleast one transmission block of only the first zone. In some embodimentsthe control channel information is transmitted in at least onetransmission block of only the second zone. It is to be understood thatthe position of the control channel is implementation specific and isnot limited to a first OFDM symbol location in each seven OFDM symbolduration as shown in FIG. 6. While only four control channels are shownin FIG. 6 it is to be understood that in some embodiments the number ofcontrol channels is dependent upon the number of OFDM symbols persub-band and/or the number of OFDM symbols in a frame.

In some embodiments, the control channel is located at the same locationin each seven OFDM symbol duration for each zone in the FDM Based ZonePartition pattern. In some embodiments, the control channel is locatedin a different location in each seven OFDM symbol duration for eachdifferent zone in the FDM Based Zone Partition pattern. In someembodiments, in a same zone, but for different sub-bands, the controlchannel is located at a different position in the seven OFDM symbolduration.

The FDM Based Zone Partition pattern 1000 includes groupings of fourpilot symbols 1040,1050, one pilot symbol for each antenna. For thefirst zone 1010, the OFDM MIMO zone, the grouping of pilot symbols 1040are common pilot symbols so that any receiver can receive and detect thepilot symbols in this zone. For the second zone 1020, the OFDM beamforming zone, the pilot symbols 1050 are dedicated pilot symbols so thatonly receivers aware of the pre-processing technique used on the pilotsutilize the dedicated pilot symbols in this zone.

The example of FIG. 6 illustrates pilot symbols that are inserted inboth an OFDM symbol containing control channel information and the datasymbol portion of the sub-bands in respective zones, as well as to thedata symbol portion only. In some embodiments pilot information isinserted in only OFDM symbols containing control channel information forrespective zone. In some embodiments pilot information is inserted inonly the data symbol portions of the respective zones. In someembodiments pilot information is inserted in both OFDM symbolscontaining control channel information and the data symbol portions ofthe respective zones.

In FIG. 6, in the frequency direction there are two consecutive twelvesubcarrier MIMO zone sub-bands each having a seven OFDM symbol durationfollowed by two consecutive twelve subcarrier beam forming zonesub-bands each having a seven OFDM symbol duration. The pattern isrepeated again in the time direction with a seven OFDM symbol period.More generally, an arrangement in the frequency direction for a firstzone and a second zone is implementation specific and may include of anynumber of sub-bands of a first zone followed by any number of sub-bandsof a second zone. In some embodiments this pattern may repeat multipletimes per frame. Similarly, with an arrangement in the time directionthe period of the pattern is implementation specific and may include aperiod having any duration of OFDM symbols.

For each twelve subcarrier sub-band having a seven OFDM symbol duration,either in the MIMO zone or the beam forming zone, FIG. 6 shows twogroupings of pilot symbols. The groupings of pilot symbols, both commonand dedicated are shown to be a two subcarrier by two symbol durationblock. It is to be understood by those skilled in the art that otherpatterns for the grouping of pilot symbols may be used. For example,other patterns may include a single subcarrier by four symbol durationblock or a four subcarrier by single symbol duration block. In someembodiments a grouping of pilot symbols is one in which only some of thepilot symbols are directly adjacent to one another. In some embodimentsa grouping of pilot symbols is one in which none of the pilot symbolsare directly adjacent to one another, but are close enough together toensure that there is time coherence and/or frequency coherence.

In some embodiments common pilot symbols may be included in the blocksthat have predominantly dedicated pilot symbols to allow receivers notcapable of detecting the dedicated pilot symbol an opportunity todetermine channel quality measurements in those blocks.

FIG. 6 is described as being for a transmitter with four antennas. It isto be understood that a four antenna transmitter is a particular exampleand not meant to limit the scope of the invention. The number ofantennas in a transmitter is an implementation specific variable. Insome embodiments of the invention the FDM based zone partition patternconcept can be applied to any number of antenna equal to or greater thanone. In some embodiments the number of pilot symbols in a grouping inthe FDM Based Zone Partition patterns is dependent on the number ofantennas in the transmitter.

In FIG. 6, in the first zone 1010, the groupings of common pilot symbols1040 are inserted in a diamond lattice pattern. Similarly, in the secondzone 1020, the groupings of dedicated pilot symbols 1050 are insertedusing a diamond lattice pattern with a similar spacing as the pilotgroups in the first zone 1010. In the illustrated example four of everyseven OFDM symbols carry encoded pilot symbols, but it is to beunderstood that depending on how pilot symbols are inserted in thesub-bands and/or frame that the ratio of OFDM symbols having pilotsymbols to OFDM symbols not having pilot symbols may vary.

In some embodiments the diamond lattice pattern in which each groupingof encoded pilot symbols, either common or dedicated is inserted withinthe OFDM frame is a perfect diamond lattice pattern. This can be achievein the same manner as that described for the TDM case described above.

A different pilot pattern can be used, as long as the same pilot patternis used for each of the pilot symbols corresponding to a particularantenna of the grouping of pilot symbols, and as long as the pilotpatterns for the encoded pilot symbols are offset from each other in thetime direction of the OFDM frame. For example, a regular diagonallattice pattern may be used; the diamond shaped lattice being a specialcase of this.

More generally, any staggered pattern of pilot symbols can be used. Insome embodiments the groupings of pilot symbols are close enoughtogether to ensure that there is time coherence and/or frequencycoherence. Time coherence occurs when pilot symbols in the timedirection are close enough in proximity that channel characteristics aresubstantially the same at the two points in time within an acceptabletolerance. Frequency coherence occurs when pilot symbols in thefrequency direction are close enough in proximity that channelcharacteristics are substantially the same at two sub-carriers within anacceptable tolerance.

In some embodiments the respective pilot patterns that are used in thezone containing common pilot symbols and the zone containing dedicatedpilot symbols are different pilot patterns.

While FIGS. 2 and 5 have generally been used to describe TDM Based ZonePartition patterns and FDM Based Zone Partition patterns respectively,it is to be understood that in some embodiments a combined TDM/FDM BasedZone Partition pattern is also considered to be within the scope of theinvention. In some embodiments a zone is allocated the entire frequencyspectrum allocated for transmission, as shown in FIG. 2. In someembodiments a zone allocated for transmission of common pilot symbols isallocated at least one sub-band of the frequency spectrum, allowing azone allocated for transmission of dedicated pilot symbols to utilizeunused sub-bands of the frequency spectrum, as shown in FIG. 5. FIG. 7illustrates an example of a combined TDM/FDM Based Zone Partitionpattern 1100 for transmitting data and pilot symbols in a transmitterwith four antennas. However, the particular pattern of FIG. 7 is notmeant to limit the scope of the invention to only four antennas. In someembodiments of the invention the TDM/FDM based zone partition patternconcept can be applied to any number of antenna.

The combined TDM/FDM Based Zone Partition pattern 1100 is shown having atwo dimensional appearance in which the horizontal direction isfrequency and the vertical direction is time. Each discrete verticalcolumn represents a single sub-carrier. Each discrete horizontal rowrepresents an OFDM symbol.

In FIG. 7, combined TDM/FDM Based Zone Partition pattern 1100 iscomprised of nine discrete time-frequency blocks in a three by threematrix that are either a first zone 1110 or a second zone 1120. Theblocks each have a sub-band of six sub-carriers and a TTI of sevensymbols. In a first sub-band, two transmission blocks of a first zone inthe time direction are followed by a third block that is a transmissionblock of a second zone. In a second sub-band, first and third blocks inthe time direction are for transmission of a second zone and a secondblock is for transmission of a first zone. In a third sub-band, firstand third blocks in the time direction are for transmission of a firstzone and a second block is for transmission of a second zone.

More generally, the number of sub-carriers in a sub-band of the blockand OFDM symbols in a TTI of the block are implementation specific andmay be more or less than the twelve sub-carriers and/or seven OFDMsymbols shown in FIG. 7. Furthermore, the allocation of respective zonesin the combined TDM/FDM Based Zone Partition pattern is implementationspecific. In some embodiments the respective zone may have a repeatingpattern in the frame. In other embodiments the respective zone fill aframe without a repeating pattern. In some embodiments, the number ofOFDM symbols in each block comprise an odd number of OFDM symbols perzone in accordance with 3GPP TR 25.814 v0.1.1 (June 2005).

TDM/FDM Based Zone Partition pattern 1100 has three OFDM symbolsallocated as control channels 1130. Each control channel occurs acrossthe three sub-bands at a same OFDM symbol location in each respectiveblock. While only three control channels are shown in FIG. 7 it is to beunderstood that in some embodiments the number of control channels isdependent upon duration of OFDM symbols per block and/or the number ofblocks in a frame.

In some embodiments pilot information is transmitted in only OFDMsymbols containing control channel information for each zone. In someembodiments pilot information is transmitted in only the portions of thezone containing data symbols. In some embodiments pilot information istransmitted in both OFDM symbols containing control channel informationand the portions of the zone containing data symbols.

In some embodiments the first and second zones are an OFDM MIMO zone andan OFDM beam forming zone, respectively. However, it is to be understoodthat this is an example of two zones and that this example is notintended to limit the scope of the invention.

For the purposes of providing context for embodiments of the inventionfor use in a communication system, FIG. 8 shows a base stationcontroller (BSC) 10 which controls wireless communications withinmultiple cells 12, which cells are served by corresponding base stations(BS) 14. In general, each base station 14 facilitates communicationsusing OFDM with mobile and/or wireless terminals 16, which are withinthe cell 12 associated with the corresponding base station 14. Themovement of the mobile terminals 16 in relation to the base stations 14results in significant fluctuation in channel conditions. Asillustrated, the base stations 14 and mobile terminals 16 may includemultiple antennas to provide spatial diversity for communications.

A high level overview of the mobile terminals 16 and base stations 14upon which aspects of the present invention may be implemented isprovided below. With reference to FIG. 9, a base station 14 isillustrated. The base station 14 generally includes a control system 20,a baseband processor 22, transmit circuitry 24, receive circuitry 26,multiple antennas 28, and a network interface 30. The receive circuitry26 receives radio frequency signals bearing information from one or moreremote transmitters provided by mobile terminals 16 (illustrated in FIG.8). A low noise amplifier and a filter (not shown) may cooperate toamplify and remove broadband interference from the signal forprocessing. Down-conversion and digitization circuitry (not shown) willthen down-convert the filtered, received signal to an intermediate orbaseband frequency signal, which is then digitized into one or moredigital streams.

The baseband processor 22 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 22 is generallyimplemented in one or more digital signal processors (DSPs) orapplication-specific integrated circuits (ASICs). The receivedinformation is then sent across a wireless network via the networkinterface 30 or transmitted to another mobile terminal 16 serviced bybase station 14.

On the transmit side, the baseband processor 22 receives digitized data,which may represent voice, data, or control information, from thenetwork interface 30 under the control of control system 20, and encodesthe data for transmission. The encoded data is output to the transmitcircuitry 24, where it is modulated by a carrier signal having a desiredtransmit frequency or frequencies. A power amplifier (not shown) willamplify the modulated carrier signal to a level appropriate fortransmission, and deliver the modulated carrier signal to the antennas28 through a matching network (not shown). Various modulation andprocessing techniques available to those skilled in the art are used forsignal transmission between the base station and the mobile terminal.

With reference to FIG. 10, a mobile terminal 16 configured according toone embodiment of the present invention is illustrated. Similarly to thebase station 14, the mobile terminal 16 will include a control system32, a baseband processor 34, transmit circuitry 36, receive circuitry38, multiple antennas 40, and user interface circuitry 42. The receivecircuitry 38 receives radio frequency signals bearing information fromone or more base stations 14. A low noise amplifier and a filter (notshown) may cooperate to amplify and remove broadband interference fromthe signal for processing. Down-conversion and digitization circuitry(not shown) will then down-convert the filtered, received signal to anintermediate or baseband frequency signal, which is then digitized intoone or more digital streams.

The baseband processor 34 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 34 is generallyimplemented in one or more digital signal processors (DSPs) andapplication specific integrated circuits (ASICs).

For transmission, the baseband processor 34 receives digitized data,which may represent voice, data, or control information, from thecontrol system 32, which it encodes for transmission. The encoded datais output to the transmit circuitry 36, where it is used by a modulatorto modulate a carrier signal that is at a desired transmit frequency orfrequencies. A power amplifier (not shown) will amplify the modulatedcarrier signal to a level appropriate for transmission, and deliver themodulated carrier signal to the antennas 40 through a matching network(not shown). Various modulation and processing techniques available tothose skilled in the art are used for signal transmission between themobile terminal and the base station.

In OFDM modulation, the transmission band is divided into multiple,orthogonal carrier waves. Each carrier wave is modulated according tothe digital data to be transmitted. Because OFDM divides thetransmission band into multiple carriers, the bandwidth per carrierdecreases and the modulation time per carrier increases. Since themultiple carriers are transmitted in parallel, the transmission rate forthe digital data, or symbols, on any given carrier is lower than when asingle carrier is used.

OFDM modulation utilizes the performance of an Inverse Fast FourierTransform (IFFT) on the information to be transmitted. For demodulation,the performance of a Fast Fourier Transform (FFT) on the received signalrecovers the transmitted information. In practice, the IFFT and FFT areprovided by digital signal processing carrying out an Inverse DiscreteFourier Transform (IDFT) and Discrete Fourier Transform (DFT),respectively. Accordingly, the characterizing feature of OFDM modulationis that orthogonal carrier waves are generated for multiple bands withina transmission channel. The modulated signals are digital signals havinga relatively low transmission rate and capable of staying within theirrespective bands. The individual carrier waves are not modulateddirectly by the digital signals. Instead, all carrier waves aremodulated at once by IFFT processing.

In operation, OFDM is preferably used for at least down-linktransmission from the base stations 14 to the mobile terminals 16. Eachbase station 14 is equipped with “n” transmit antennas 28, and eachmobile terminal 16 is equipped with “m” receive antennas 40. Notably,the respective antennas can be used for reception and transmission usingappropriate duplexers or switches and are so labeled only for clarity.

With reference to FIG. 11, a logical OFDM transmission architecture willbe described. Initially, the base station controller 10 will send datato be transmitted to various mobile terminals 16 to the base station 14.The base station 14 may use the channel quality indicators (CQIs)associated with the mobile terminals to schedule the data fortransmission as well as select appropriate coding and modulation fortransmitting the scheduled data. The CQIs may be directly from themobile terminals 16 or determined at the base station 14 based oninformation provided by the mobile terminals 16. In either case, the CQIfor each mobile terminal 16 is a function of the degree to which thechannel amplitude (or response) varies across the OFDM frequency band.

Scheduled data 44, which is a stream of bits, is scrambled in a mannerreducing the peak-to-average power ratio associated with the data usingdata scrambling logic 46. A cyclic redundancy check (CRC) for thescrambled data is determined and appended to the scrambled data usingCRC adding logic 48. Next, channel coding is performed using channelencoder logic 50 to effectively add redundancy to the data to facilitaterecovery and error correction at the mobile terminal 16. Again, thechannel coding for a particular mobile terminal 16 is based on the CQI.In some implementations, the channel encoder logic 50 uses known Turboencoding techniques. The encoded data is then processed by rate matchinglogic 52 to compensate for the data expansion associated with encoding.

Scheduled data 44, which is a stream of bits, is scrambled in a mannerreducing the peak-to-average power ratio associated with the data usingdata scrambling logic 46. A cyclic redundancy check (CRC) for thescrambled data is determined and appended to the scrambled data usingCRC adding logic 48. Next, channel coding is performed using channelencoder logic 50 to effectively add redundancy to the data to facilitaterecovery and error correction at the mobile terminal 16. Again, thechannel coding for a particular mobile terminal 16 is based on the CQI.In some implementations, the channel encoder logic 50 uses known Turboencoding techniques. The encoded data is then processed by rate matchinglogic 52 to compensate for the data expansion associated with encoding.

Bit interleaver logic 54 systematically reorders the bits in the encodeddata to minimize the loss of consecutive data bits. The resultant databits are systematically mapped into corresponding symbols depending onthe chosen baseband modulation by mapping logic 56. Preferably,Quadrature Amplitude Modulation (QAM) or Quadrature Phase Shift Key(QPSK) modulation is used. The degree of modulation is preferably chosenbased on the CQI for the particular mobile terminal. The symbols may besystematically reordered to further bolster the immunity of thetransmitted signal to periodic data loss caused by frequency selectivefading using symbol interleaver logic 58.

At this point, groups of bits have been mapped into symbols representinglocations in an amplitude and phase constellation. When spatialdiversity is desired, blocks of symbols are then processed by space-timeblock code (STC) encoder logic 60, which modifies the symbols in afashion making the transmitted signals more resistant to interferenceand more readily decoded at a mobile terminal 16. In some embodimentsthe STC encoder logic 60 encodes the data to be sent in the common pilotsymbol zone using open-loop MIMO. In some embodiments this may involvecreation of a pre-processing matrix that is consistent with open-loopMIMO. For example, such a pre-processing matrix may be the identitymatrix, which would effectively result in the appearance of nopre-processing being performed. In some embodiments as a part ofinserting data and common pilot symbols in the second zone, the STCencoder logic 60 creates a pre-processing matrix that is consistent withclosed loop MIMO, such as beam forming for encoding the data and pilotsymbols to be sent in the common pilot symbol zone.

While STC encoder logic 60 is shown as a single bock in FIG. 11, it isto be understood that the processes of partitioning OFDM frames,allocating the first and second zones, and inserting data and commonpilot symbols in the first zone and data and dedicated pilot symbols inthe second zone may be represented by separate logic blocks.

The STC encoder logic 60 will process the incoming symbols and provide“n” outputs corresponding to the number of transmit antennas 28 for thebase station 14. The control system 20 and/or baseband processor 22 asdescribed above with respect to FIG. 9 will provide a mapping controlsignal to control STC encoding. At this point, assume the symbols forthe “n” outputs are representative of the data to be transmitted andcapable of being recovered by the mobile terminal 16.

In some embodiments, the control system 20 and/or baseband processor 22will send a mapping control signal that defines the partition of OFDMframes for N transmission antennas, defines the allocation of first andsecond zones in the respective OFDM frames, and controls insertion of atwo dimensional array of data and common pilot symbols in time-frequencyin the first zone for transmission of common pilot symbols and insertionof a two dimensional array of data and dedicated pilot symbols intime-frequency in the second zone for transmission of dedicated pilotsymbols.

For the present example, assume the base station 14 has two antennas 28(n=2) and the STC encoder logic 60 provides two output streams ofsymbols. Accordingly, each of the symbol streams output by the STCencoder logic 60 is sent to a corresponding IFFT processor 62,illustrated separately for ease of understanding. Those skilled in theart will recognize that one or more processors may be used to providesuch digital signal processing, alone or in combination with otherprocessing described herein. The IFFT processors 62 will preferablyoperate on the respective symbols to provide an inverse FourierTransform. The output of the IFFT processors 62 provides symbols in thetime domain. The time domain symbols are grouped into frames, which areassociated with a prefix by prefix insertion logic 64. Each of theresultant signals is up-converted in the digital domain to anintermediate frequency and converted to an analog signal via thecorresponding digital up-conversion (DUC) and digital-to-analog (D/A)conversion circuitry 66. The resultant (analog) signals are thensimultaneously modulated at the desired RF frequency, amplified, andtransmitted via the RF circuitry 68 and antennas 28. Notably, pilotsignals known by the intended mobile terminal 16 are scattered among thesub-carriers. The mobile terminal 16, which is discussed in detailbelow, will use the pilot signals for channel estimation.

Reference is now made to FIG. 12 to illustrate reception of thetransmitted signals by a mobile terminal 16. Upon arrival of thetransmitted signals at each of the antennas 40 of the mobile terminal16, the respective signals are demodulated and amplified bycorresponding RF circuitry 70. For the sake of conciseness and clarity,only one of the two receive paths is described and illustrated indetail. Analog-to-digital (A/D) converter and down-conversion circuitry72 digitizes and down-converts the analog signal for digital processing.The resultant digitized signal may be used by automatic gain controlcircuitry (AGC) 74 to control the gain of the amplifiers in the RFcircuitry 70 based on the received signal level.

Initially, the digitized signal is provided to synchronization logic 76,which includes coarse synchronization logic 78, which buffers severalOFDM symbols and calculates an auto-correlation between the twosuccessive OFDM symbols. A resultant time index corresponding to themaximum of the correlation result determines a fine synchronizationsearch window, which is used by fine synchronization logic 80 todetermine a precise framing starting position based on the headers. Theoutput of the fine synchronization logic 80 facilitates frameacquisition by frame alignment logic 84. Proper framing alignment isimportant so that subsequent FFT processing provides an accurateconversion from the time domain to the frequency domain. The finesynchronization algorithm is based on the correlation between thereceived pilot signals carried by the headers and a local copy of theknown pilot data. Once frame alignment acquisition occurs, the prefix ofthe OFDM symbol is removed with prefix removal logic 86 and resultantsamples are sent to frequency offset correction logic 88, whichcompensates for the system frequency offset caused by the unmatchedlocal oscillators in the transmitter and the receiver. Preferably, thesynchronization logic 76 includes frequency offset and clock estimationlogic 82, which is based on the headers to help estimate such effects onthe transmitted signal and provide those estimations to the correctionlogic 88 to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready forconversion to the frequency domain using FFT processing logic 90. Theresults are frequency domain symbols, which are sent to processing logic92. The processing logic 92 extracts the scattered pilot signal usingscattered pilot extraction logic 94, determines a channel estimate basedon the extracted pilot signal using channel estimation logic 96, andprovides channel responses for all sub-carriers using channelreconstruction logic 98. In order to determine a channel response foreach of the sub-carriers, the pilot signal is essentially multiple pilotsymbols that are scattered among the data symbols throughout the OFDMsub-carriers in a known pattern in both time and frequency. Examples ofscattering of pilot symbols among available sub-carriers over a giventime and frequency plot in an OFDM environment are found in PCT PatentApplication No. PCT/CA2005/000387 filed Mar. 15, 2005 assigned to thesame assignee of the present application. Continuing with FIG. 12, theprocessing logic compares the received pilot symbols with the pilotsymbols that are expected in certain sub-carriers at certain times todetermine a channel response for the sub-carriers in which pilot symbolswere transmitted. The results are interpolated to estimate a channelresponse for most, if not all, of the remaining sub-carriers for whichpilot symbols were not provided. The actual and interpolated channelresponses are used to estimate an overall channel response, whichincludes the channel responses for most, if not all, of the sub-carriersin the OFDM channel.

The frequency domain symbols and channel reconstruction information,which are derived from the channel responses for each receive path areprovided to an STC decoder 100, which provides STC decoding on bothreceived paths to recover the transmitted symbols. The channelreconstruction information provides equalization information to the STCdecoder 100 sufficient to remove the effects of the transmission channelwhen processing the respective frequency domain symbols.

The recovered symbols are placed back in order using symbolde-interleaver logic 102, which corresponds to the symbol interleaverlogic 58 of the transmitter. The de-interleaved symbols are thendemodulated or de-mapped to a corresponding bitstream using de-mappinglogic 104. The bits are then de-interleaved using bit de-interleaverlogic 106, which corresponds to the bit interleaver logic 54 of thetransmitter architecture. The de-interleaved bits are then processed byrate de-matching logic 108 and presented to channel decoder logic 110 torecover the initially scrambled data and the CRC checksum. Accordingly,CRC logic 112 removes the CRC checksum, checks the scrambled data intraditional fashion, and provides it to the de-scrambling logic 114 forde-scrambling using the known base station de-scrambling code to recoverthe originally transmitted data 116.

In parallel to recovering the data 116, a CQI 120, or at leastinformation sufficient to create a CQI 120 at the base station 14, isdetermined and transmitted to the base station 14. As noted above, theCQI 120 may be a function of the carrier-to-interference ratio (CIR122), as well as the degree to which the channel response varies acrossthe various sub-carriers in the OFDM frequency band. Such variation canbe determined by channel variation analysis 118. The channel gain foreach sub-carrier in the OFDM frequency band being used to transmitinformation is compared relative to one another to determine the degreeto which the channel gain varies across the OFDM frequency band.Although numerous techniques are available to measure the degree ofvariation, one technique is to calculate the standard deviation of thechannel gain for each sub-carrier throughout the OFDM frequency bandused to transmit data.

FIGS. 7 to 12 each provide a specific example of a communication systemor elements of a communication system that could be used to implementembodiments of the invention. It is to be understood that embodiments ofthe invention can be implemented with communications systems havingarchitectures that are different than the specific example, but thatoperate in a manner consistent with the implementation of embodiments asdescribed herein.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

What is claimed is: 1.-20. (canceled)
 21. An apparatus, comprising: a baseband processor configured to process at least a portion of a signal received via a wireless channel, wherein the signal includes: a plurality of successive Orthogonal Frequency Division Multiplexing (OFDM) symbols grouped into a plurality of transmission time intervals; a plurality of successive blocks that each include an even number of the transmission time intervals; data and common pilot symbols being inserted in a pre-defined time-frequency pattern across multiple ones of the plurality of successive blocks, wherein common pilot symbols are for use by a plurality of receivers and are inserted in a diamond shaped lattice pattern across subcarriers and OFDM symbols in each block, wherein the diamond pattern comprises a regular diagonal pattern, and wherein the common pilots symbols are inserted in both a control portion and a data portion of each block according to the diamond shaped lattice pattern; and wherein the baseband processor is configured to process the common pilot symbols to determine channel information for the wireless channel.
 22. The apparatus of claim 21, wherein each of the plurality of successive blocks include two transmission time intervals.
 23. The apparatus of claim 21, wherein the diamond shaped lattice pattern is a perfect diamond shaped lattice pattern.
 24. The apparatus of claim 21, wherein the baseband processor is further configured to process dedicated pilot symbols for the apparatus that are included on ones of the plurality of successive blocks.
 25. The apparatus of claim 24, wherein the common and dedicated pilot symbols have different transmission power.
 26. The apparatus of claim 25, wherein at least one block uses a first multiple input multiple output (MIMO) format and at least one other block uses at least one other MIMO format.
 27. A non-transitory computer-readable medium having instructions stored thereon that are executable by a computing device to perform operations comprising: processing at least a portion of a signal received via a wireless channel, wherein the signal includes: a plurality of successive Orthogonal Frequency Division Multiplexing (OFDM) symbols grouped into a plurality of transmission time intervals; a plurality of successive blocks that each include an even number of the transmission time intervals; data and common pilot symbols being inserted in a pre-defined time-frequency pattern across multiple ones of the plurality of successive blocks, wherein common pilot symbols are for use by a plurality of receivers and are inserted in a diamond shaped lattice pattern across subcarriers and OFDM symbols in each block, wherein the diamond pattern comprises a regular diagonal pattern, and wherein the common pilots symbols are inserted in both a control portion and a data portion of each block according to the diamond shaped lattice pattern; and processing the common pilot symbols to determine channel information for the wireless channel.
 28. The non-transitory computer-readable medium of claim 27, wherein each of the plurality of successive blocks include two transmission time intervals.
 29. The non-transitory computer-readable medium of claim 27, wherein the diamond shaped lattice pattern is a perfect diamond shaped lattice pattern.
 30. The non-transitory computer-readable medium of claim 27, wherein the further comprise processing dedicated pilot symbols for the computing device that are included on ones of the plurality of successive blocks.
 31. The non-transitory computer-readable medium of claim 27, wherein the common and dedicated pilot symbols have different transmission power.
 32. An apparatus, comprising: a baseband processor configured to process at least a portion of a signal received via a wireless channel, wherein the signal includes: a plurality of successive Orthogonal Frequency Division Multiplexing (OFDM) symbols grouped into a plurality of transmission time intervals; a plurality of successive blocks, wherein each block consists of twelve (12) sub-carriers over one of the plurality of transmission time intervals; data and common pilot symbols being inserted in a pre-defined time-frequency pattern across multiple ones of the plurality of successive blocks, wherein common pilot symbols are for use by a plurality of receivers, and wherein the common pilots symbols are inserted in both a control portion and a data portion of each block; dedicated pilot symbols being inserted in a pre-defined time-frequency pattern across one or more of the plurality of successive blocks and are inserted in a diamond shaped lattice pattern across subcarriers and OFDM symbols in each block, wherein the diamond shaped lattice pattern is a regular diagonal pattern, wherein the common pilots symbols are inserted in the data portion of each block according to the diamond shaped lattice pattern; and wherein the dedicated pilot symbols are dedicated for use by the apparatus; wherein the baseband processor is configured to process the common pilot symbols to determine channel information for the wireless channel.
 33. The apparatus of claim 32, wherein the diamond shaped lattice pattern is a perfect diamond shaped lattice pattern.
 34. The apparatus of claim 32, wherein the common pilot symbols are inserted in a second diamond shaped lattice pattern across subcarriers and OFDM symbols in each block.
 35. The apparatus of claim 34, wherein the second diamond shaped lattice pattern is offset from the dedicated pilot symbol pattern.
 36. The apparatus of claim 35, wherein the second diamond shaped lattice pattern comprises a regular diagonal pattern.
 37. The apparatus of claim 32, wherein at least one block uses a first multiple input multiple output (MIMO) format and at least one other block uses at least one other MIMO format. 